The store is in business to make money. Because of the shortage, they don't have much to sell and often have no idea when new stock might be coming in. If they price items at "normal" prices, they sell out for less than they could get and now they have nothing to sell.

If they raise prices, then that makes up for the loss of stock. But if they raise them too much people stop buying at all and then the prices will eventually fall.

Since the items that they are raising the prices on aren't life support related like water, batteries, etc. that might go up when preparing for a hurricane, I have no problem with it.